Matt (in the comments) argues that the reason that it is tempting to focus upon Guantanamo Bay while leaving the butchery in Darfur uncommented on is that an elected Government can be lobbied, but there is no point in commenting on the activities of unelected ones as there is little that can be done to alter their behaviour.
This, to my dull eye, explains the difference between the 'pro-liberation Left' and the rest of the left-liberal consensus.
I thought I'd do a quick bit of research on this. The search function on Blogspot sites is a bit flaky, so I can't do this test on them. Ditto Typepad. But I've found one site that takes a critical view of the current Government's foreign policy. I don't mean to particularly pick on Bloggerheads, but - well, when your search function works properly, you open yourself to all sorts of criticism:
Here are some search results:
Search term: Guantanamo: 33 results
Search term: Darfur: .....